Field of the Disclosure
The present invention relates to hearing enhancement devices and hearing enhancement by selected electronic amplification of frequency bands input at select ear locations.
Related Art
An estimated 5-10% of the U.S. population, and more that 50% of the population over sixty years of age, has hearing loss, primarily of high frequencies. Similar numbers have been stated for other parts of the world, such as India. The largest population of people with hearing impairment have normal hearing in the low frequency ranges and hearing loss in the higher frequency ranges. Most problematic for people with mild hearing loss are high frequency sounds.
Most hearing aids have their amplifying transducer fitted into the ear canal (the external auditory canal). They employ signal processing techniques to rebuild sounds throughout the usable frequency range of the user. A drawback is that such hearing aids typically block the outer ear and ear canal to prevent feedback and whistling since the higher gains, greater than 30 db which are used to allow a user to have better speech comprehension feed back from the amplifying transducer to the hearing aid microphone if the transducer is not sealed off in the ear canal. Conventional hearing aids can unnecessarily amplify sound in a manner that may be uncomfortable and annoying for users with mild hearing loss. Also, they may introduce phase shifts to received sounds, resulting in a reduction of the user's ability to localize sound sources. Sounds of high amplitude may be distorted by the sound processing circuitry. In addition, such devices may produce an occlusion effect, due to transmission of sound by tissue conduction as a result of the blockage of the ear canal and impedance of air conduction. This can have the effect of increased loudness of some frequency ranges, resulting in sounds that seem unnatural and uncomfortable, and the user may not even recognize his own voice.
With such devices, electronic frequency band matched amplitude amplification to match the patient's hearing is difficult, particularly where the user still has reasonably normal hearing at least at lower frequencies of the natural ambient sound field. This is because distortion and over-amplification of background noise can occur and is difficult to eliminate to provide the same experience as the user's natural hearing.
The entire contents of U.S. Pat. No. 7,916,884, issued Mar. 29, 2011, U.S. Pat. No. 8,750,547, issued Jun. 10, 2014, U.S. Pat. No. 5,987,146, issued Nov. 16, 1999, U.S. Pat. Nos. 4,904,708, 5,276,739, 5,278,912, and 5,488,668, 9,167,364 and PCT International Application No. PCT/US03/14973, filed May 12, 2003, are incorporated in full herein by reference.
For good or acceptable human voice or word comprehension, many patients need only a small boost of higher frequencies, which is where most of the hearing loss in later life occurs. In particular, hearing loss at higher frequencies is often in the range of 30 dB or more. Amplification at such levels often results in whistle and feedback. This is generally dealt with by sealing the hearing aid speaker transducer to the wall of the auditory canal. Natural hearing, even in the portions of the spectrum for which there is little of no hearing impairment, must thus be foregone. Vent holes are sometimes provided to allow through some normal sound, but there is still substantial attenuation of ambient sound waves.
As a consequence, many persons with only high frequency hearing impairment find electronic hearing aids to be unsatisfactory, and simply accept the impairment as an unavoidable consequence of aging.
A need exists for an improved hearing enhancement device usable by those with high frequency hearing impairment for whom existing amplified devices are not completely satisfactory and that avoids the problems discussed above.